Utilizing the Colorado Lightning Mapping Array (COLMA) for Discriminating Hail Size

Of the many threats posed by thunderstorms, none can quite compare to the severe hail that annually plagues the eastern Rocky Mountains and western high plains. Nearly every year, hail to the size of softballs falls on at least one community in the Cheyenne National Weather Service county warning area, but with each location in the region facing nearly six hail days per year and an average hailstone size of 1.2 inches, widespread damage often ensues (Changon et. al). NASA's Short-term Prediction Research and Transition (SPoRT) is attempting to better understand the lightning cycles in thunderstorms through its collaboration with eight Lightning Mapping Arrays (LMAs) throughout the United States, including the Colorado Lightning Mapping Array (COLMA). This project utilizes COLMA data from Colorado State University and SPoRT both in the raw flash density (RFD) or source form along with the further-processed flash extent density (FED) form. Lightning flash jumps occur in both the RFD and FED forms and work as indicators to the strengthening of updrafts in thunderstorms, as results from the Northern Alabama Lightning Mapping Array (NALMA) have shown. Conditions in the high plains often differ though and the density of measured lightning sources is usually much less than that in the Deep South. Storm event dates were compared with COLMA data and archived radar feed for thunderstorms that produced large hail in excess of two inches, hail between one and two inches, and hail under one inch. From this list, an average lead-time was found from the initial RFD and FED jumps to the spotter-reported hail times. Though the RFD and FED magnitudes differed from storm to storm, an average percentage jump could be computed for each. The incorporation of this information could further enhance the warning decision process, especially in between radar updates. The results of this project should aid the National Weather Service in the protection of life and property through extending lead-times and in turn, promote a more Weather-Ready Nation.